4

Shimano sprockets are marked with short strings like "aq/ar", "bg", "as/au/be" and others. For example, "bj bk" can be read on the image below:

bj/bk marks

It looks like they mean the hyperglide series to which this sprocket belongs. Is there anywhere a list of these series?

  • 15T means 15 teeth (can be verified by counting). But the rest: no idea... – anderas Dec 1 '16 at 14:03
  • @anderas I updated the question to mention that I understand the part "15T" and ask about the part "bj bk" :-) – Konstantin Shemyak Dec 1 '16 at 14:06
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According to this post they appear to be date codes. There is a list of date codes here. They are outdated, but you can follow the pattern to figure out when the sprocket was made. the one in your picture appears to be from October/November 2001 if this theory is correct. This site has a more recent list indicating that this trend has continued. The date codes from that page are partially copied below in case those old forums disappear.

This doesn't appear to make sense with codes like aq/ar, but the codes on the sprocket shown most likely indicate date of manufacturer. AQ/AR may indicate the model of cassette they came from. Shimano documentation says that ar is associated with the CS-HG400 9 speed sprockets. AQ seems to be associated with the CS-M770 cassette. If you google the specific code you are looking for, such as "shimano code aq" (without quotes) you will most likely find shimano documentation for the part in question.

MONTH
A JAN
B FEB
C MAR
D APR
E MAY
F JUN
G JUL
H AUG
I SEP
J OCT
K NOV
L DEC

YEAR
X 1999
Y 2000
Z 2001
A 2002
B 2003
C 2004
D 2005
E 2006
F 2007
G 2008
H 2009
I 2010
J 2011
K 2012
L 2013
M 2014

  • 1
    Thank you for the detailed answer. But I do not believe that namely these sprocket codes refer to manufacturing year. For example I have some sprockets with 'aq' mark which are from beginning of this century, and 'aq' cassette is in Shimano manual from 2014 which you linked. The manual specifically says "aq teeth combination". – Konstantin Shemyak Dec 1 '16 at 20:07
  • Yes, The second part of my answer would probably apply more. Look in Google for Shimano Code AQ PDF and the correct result alwasy seems to show up on top. The BJ / BK from the example is from the Deore XT CS-M771 sprockets . – Kibbee Dec 1 '16 at 20:34
  • I suspect it has to do with the cassette its from. Sheldon's gear calculator says an "ab" is a 11-19 7 speed cassette, an "ai" is 11-24, and "ac" is 11-28 7 speed cassette. aq and ar are both llisted as 11-32 9 speed cassette. – Criggie Dec 1 '16 at 22:58

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